Violin Distributions

import {
    type ChartPoint,
    binY,
    d3AreaXCurve,
    defineChart,
    dot,
    groupBy,
    median,
    normalize,
    tickY,
    violinY,
} from "@tanstack/charts";
import { motion } from "@tanstack/charts/motion";
import { tooltip } from "@tanstack/charts/tooltip";
import { Chart } from "@tanstack/react-charts/core";
import { useMemo } from "react";

import { scaleLinear, scalePoint } from "d3-scale";
import { curveBasis } from "d3-shape";
import { SlidersHorizontal } from "lucide-react";

import { Card, CardContent, CardDescription, CardFooter, CardHeader, CardTitle } from "@/components/ui/card";

interface PenguinDatum {
    species: "Adelie" | "Chinstrap" | "Gentoo";
    body_mass_g: number;
}

const motionRenderer = motion({
    initial: "always",
    transition: { type: "spring", stiffness: 170, damping: 18, mass: 1 },
});

const speciesList: ("Adelie" | "Chinstrap" | "Gentoo")[] = ["Adelie", "Chinstrap", "Gentoo"];
const massBoundaries = [2500, 3000, 3500, 4000, 4500, 5000, 5500, 6000, 6500];

function generateDemoData(): PenguinDatum[] {
    const results: PenguinDatum[] = [];
    const means = [3700, 3730, 5080];

    speciesList.forEach((sp, idx) => {
        for (let i = 0; i < 50; i++) {
            const mass = means[idx] + (Math.random() - 0.5) * 800;
            results.push({ species: sp, body_mass_g: Math.round(mass) });
        }
    });

    return results;
}

function shadcnTooltipContent<TDatum>(points: readonly ChartPoint<TDatum>[]) {
    if (points.length === 0) return { title: "", rows: [] };
    const d = points[0].datum as { species: string; median?: number; y?: number };
    if (!d) return { title: "", rows: [] };
    if (d.median !== undefined) {
        return {
            title: `${d.species} (Median Marker)`,
            rows: [
                { label: "Median Mass", value: `${Math.round(d.median).toLocaleString()} g`, color: "var(--chart-1)" },
            ],
        };
    }
    return {
        title: `${d.species} (Violin Profile)`,
        rows: [{ label: "Mass Bin", value: `${d.y?.toLocaleString()} g`, color: "var(--chart-2)" }],
    };
}

export function ViolinDistributions() {
    const data = useMemo(() => generateDemoData(), []);

    const profiles = useMemo(() => {
        const bins = binY(data, {
            value: "body_mass_g",
            by: "species",
            thresholds: massBoundaries,
            outputs: { count: { reduce: "count" } },
        });

        return normalize(bins, {
            value: "count",
            by: "species",
            basis: "max",
            as: "width",
        });
    }, [data]);

    const summaries = useMemo(() => {
        return groupBy(data, {
            by: "species",
            outputs: {
                median: { value: "body_mass_g", reduce: median },
            },
        });
    }, [data]);

    const definition = useMemo(
        () =>
            defineChart(
                {
                    renderer: motionRenderer,
                    marks: [
                        violinY(profiles, {
                            id: "mass-violins",
                            x: "species",
                            y: "y",
                            width: "width",
                            key: (row: { species: string; y: number }) => `${row.species}:${row.y}`,
                            span: 0.76,
                            color: "species",
                            fillOpacity: 0.55,
                            curve: d3AreaXCurve(curveBasis),
                        }),
                        tickY(summaries, {
                            id: "median-ticks",
                            x: "species",
                            y: "median",
                            key: "species",
                            span: 0.36,
                            stroke: "var(--foreground)",
                            strokeWidth: 2,
                        }),
                        dot(summaries, {
                            id: "median-dots",
                            x: "species",
                            y: "median",
                            key: "species",
                            color: "species",
                            stroke: "var(--background)",
                            strokeWidth: 1.5,
                            r: 4,
                        }),
                    ],
                    scales: {
                        x: {
                            scale: scalePoint<string>().domain(speciesList).padding(0.5),
                        },
                        y: { scale: scaleLinear, grid: true, axis: { label: "Body Mass (g)" } },
                    },
                    color: {
                        domain: speciesList,
                        range: ["var(--chart-1)", "var(--chart-2)", "var(--chart-3)"],
                    },
                    margin: { top: 24, right: 24, bottom: 32, left: 45 },
                    theme: {
                        foreground: "var(--muted-foreground)",
                        grid: "var(--border)",
                        background: "transparent",
                    },
                },
                {
                    keyboard: true,
                    tooltip: {
                        use: tooltip,
                        className:
                            "font-sans shadow-none rounded-md bg-popover text-popover-foreground border p-2 text-xs",
                        anchor: "pointer",
                        placement: "auto",
                        content: (points) => shadcnTooltipContent(points),
                    },
                },
            ),
        [profiles, summaries],
    );

    return (
        <Card className="w-full max-w-xl">
            <CardHeader>
                <CardTitle>Violin Kernel Density Plot</CardTitle>
                <CardDescription>Symmetric KDE violin profiles overlaid with central median markers</CardDescription>
            </CardHeader>
            <CardContent>
                <div className="h-[250px] w-full">
                    <Chart
                        definition={definition}
                        renderer={motionRenderer}
                        height={250}
                        ariaLabel="Violin Kernel Density Plot Chart"
                    />
                </div>
            </CardContent>
            <CardFooter className="flex-col items-start gap-2 text-sm">
                <div className="flex items-center gap-2 leading-none font-medium">
                    Violin contours reveal multi-modal continuous density shapes{" "}
                    <SlidersHorizontal className="h-4 w-4 text-emerald-500" />
                </div>
                <div className="text-muted-foreground leading-none">
                    Combines boxplot median markers with smooth kernel density estimations
                </div>
            </CardFooter>
        </Card>
    );
}

export default ViolinDistributions;